The present invention relates in general to the reduction of the transmission of movement or vibrations between interconnected elements. In particular, the present invention is related to a device and method for actively controlling and reducing the transmission of unwanted vibrations between stiffly interconnected elements by responsively operating means to oppose the unwanted relative movement.
It is known that when two or more physical bodies or elements are interconnected, vibrations occurring on or being received by one body are transmitted to the second body, generally through the structures interconnecting the bodies. Examples abound, such as the transmission of the bumps in a road by the wheels to the cab of an automobile, or the transmission of the cycling of a refrigerator compressor to the frame and door of the refrigerator. Often, these transmissions are ignored and/or tolerated. Sometimes, designers attempt to reduce these vibrations (or at least their effects) by isolating one body from another. For example, both the wheels of the automobile and the compressor of a refrigerator are somewhat isolated from the remainder of their structures by the placement of springs between the source of the vibration and the remaining structure.
Additionally, other isolation devices are known, such as dampers, which "soften" the attachment of one body to another. In the present examples, automobiles usually use air pistons (called "shock absorbers") and refrigerator compressors are usually mounted on rubber pads.
In many applications, passive devices such as springs and dampers are adequate. However, in many applications, springs often introduce resonance effects which prevent proper operation of the system. Still in other systems, springs cannot reduce the transmission of vibrations sufficiently.
It is also known to isolate bodies by placing an intense magnetic field between the bodies. If one body generates the field and the other body reacts to the field, one of the bodies seems to levitate above the other. Bodies displaced by such magnetic levitation, however, generally collapse into each other if the power to generate the magnetic force is removed. In an attempt to reduce the coupling of vibrations between bodies separated by magnetic levitation, it is known to attempt to reduce the apparent stiffness between the bodies to zero; however, this technique is the equivalent to placing a small stiffness spring between the bodies, generally having the same problems as discussed above.
It is also known to provide passive viscous dampening devices in the load path between bodies. While these devices achieve some attenuation of the vibration, they generally do not prevent the transmission of the vibration.
The transmission of vibration between elements can be particularly harmful in certain environments. For example, artificial satellites often require considerable stability for pointing and measuring sensors; yet, such vehicles often also have inertial reaction wheels or reciprocating elements which regularly generate considerable amounts of vibration. In the relative vacuum of space, vibrations are not damped as they are on earth by a surrounding atmosphere and, accordingly, vibration problems are particularly difficult to remedy.
It is accordingly an object of the present invention to provide a novel device and method to obviate these and other vibration transmission problems in the prior art.
It is a further object of the present invention to provide a novel device and method to reduce the amount and severity of vibration transmitted between interconnected elements.
It is still another object of the present invention to provide a novel device and method for reducing inter-structural vibration while maintaining a stiff connection between structures.
It is yet another object of the present invention to provide a novel device and method to actively reduce vibration that would otherwise be transmitted between interconnected structures.
It is still a further object of the present invention to provide a novel device and method which reduces vibrations experienced in one direction relatively independently of vibrations experienced in other directions.
It is a still further object of the present invention to provide a novel device and method to actively reduce the transmission of inter-structural vibration while maintaining stability over a wide variety of conditions.
It is still another object of the present invention to provide a novel device and method which both reduces the transmission of inter-structural vibrations while permitting a selective alignment of the interconnected bodies.